1. Field of the Invention
One or more embodiments of the invention relates to an electromedical implant designed for determining P-wave dispersion. The electromedical implant can, for example, be an appropriately configured implantable pacemaker or an implantable cardioverter/defibrillator (ICD), or a combination of both.
2. Description of the Related Art
Electromedical implants include a recording unit for recording an electrocardiogram signal. This recording unit is connected, or can be connected, to at least two electrodes for recording electric signals, which reflect the curve of an electrocardiogram signal of the right and left atria.
In addition, the electromedical implant comprises a detection unit, which is designed to detect signal features characterizing atrial cardiac actions in an electrocardiogram signal. The latter is performed in known implantable pacemakers or ICD in that an intra-atrial electrocardiogram signal recorded in the atrium of a heart is permanently subjected to a threshold value comparison. If the amplitude of the intra-atrial electrocardiogram signal exceeds the threshold value, an atrial cardiac action is detected. Typically, an atrial sensing unit is provided for this purpose. The detection of an atrial cardiac action is also referred to an atrial sense event. The respectively detected electric signal is the result of a depolarization of the atrial muscle cells accompanying the contraction of the atrial myocardium.
Detecting and evaluating the atrial dispersion are likewise known in principle. The P-wave dispersion describes the temporal distribution of the P-wave in the 12 leads of the surface electrocardiogram and is therefore an expression of atrial excitation propagation. If the P-wave dispersion value increases, it can be assumed that inhomogeneous atrial excitation formation and conduction are present. In particular atrial excitation initiated by several focuses prior to atrial arrhythmia causes inhomogeneous excitation of the atrium and consequently greater P-wave dispersion.
P-wave dispersion therefore provides important diagnostic information for patients at risk of atrial arrhythmia. Since the coincidence of atrial fibrillation and the indication for an ICD are very high, this parameter is of tremendous importance for these patients.
US 2005/0027321 A1 describes an apparatus which, among other things, can determine the morphology of the P-wave, including the duration thereof, and is also intended to record the dispersions of widths of the P-waves. The dispersion term is used slightly differently in US 2005/0027321 A1: here, the comparison of the variance of the P-wave width recorded over several consecutive P-waves is meant.
P-wave dispersion described in the literature, however, in the 12-channel surface electrocardiogram is defined as a temporal “scattering” of a P-wave measured in the 12 leads of the surface electrocardiogram. This P-wave dispersion is therefore an expression of the atrial excitation formation and propagation. This is for example what is to be implemented with one or more embodiments of the invention in an electronic implant, without making an atrial electrode absolutely necessary as will be explained in the remainder of this disclosure.
The study “Koide Y, Yotsukura M, Ando H, Aoki S, Suzuki T, Sakata K, Ootomo E, Yoshino H. “Usefulness of P-wave dispersion in standard twelve-lead electrocardiography to predict transition from paroxysmal to persistent atrial fibrillation.” Am J. Cardiol. 2008 Sep. 1; 102(5):573-7. Epub 2008 Jul 10” reports of the diagnostic values of P-wave dispersion derived from the 12-channel surface electrocardiogram.
So far, it has not been possible to automatically capture this parameter in an ICD.